1. Field of the Invention
The present invention relates to an apparatus for forming a zirconia-based film on a substrate to be processed, such as a semiconductor wafer.
2. Description of the Related Art
Recently, due to demands for higher integration and higher operating speed of a large scale integration (LSI), design rules of semiconductor devices that constitute a LSI are becoming finer. Along with the demands, there are also demands for increased capacity of capacitors that are used in dynamic random access memories (DRAMs) and demands for increased permittivity of dielectric films. It is necessary to crystallize such dielectric films to obtain higher permittivity, and thus a film with higher crystallinity is demanded. Furthermore, since some devices have limits in thermal budget, a film which may be formed or crystallized at a low temperature is demanded.
A zirconium oxide (ZrO2) film is considered as a film with high permittivity, which is applicable to the above purposes, (see Reference 1).
Known techniques for forming a zirconium oxide film at a low temperature include an atomic layer deposition (ALD) process, in which source gas (precursor), e.g. tetrakis(ethylmethylamino)zirconium (TEMAZ), and oxidizer, e.g. O3 gas, are supplied alternately (see Reference 2). Furthermore, zirconium oxide may be easily crystallized, and may be crystallized without inflicting negative effects on a device by forming a film at a low temperature by using the technique as described above or, additionally, annealing the film at a low temperature less than or equal to 450° C.
Such a dielectric film is required to exhibit not only high permittivity but also low leakage current. However, when a dielectric film is crystallized as described above, leakage current increases due to leakage from grain boundaries of crystals.
[Reference 1] Japanese Laid-Open Patent Publication No. 2001-152339
[Reference 2] Japanese Laid-Open Patent Publication No. 2006-310754